Biocidal coating compositions and method

ABSTRACT

A biocidal film-forming composition, preferably a paint, is disclosed, comprising hydrated lime and a non-ionic polyolefinic latex resistant to hydrated-lime induced coagulation and phase separation. Also disclosed is the method of making certain such composition wherein hydrated lime is admixed with a non-ionic polyolefinic ester latex with agitation and continuing such agitation until hydrolysis of the ester is substantially completed and rheology of the composition is stabilized.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of application Ser. No. 09/137,576, filedAug. 21, 1998 now U.S. Pat. No. 6,042,638 which, in turn, is acontinuation-in-part of application Ser. No. 08/646,078 filed May 9,1996 (now abandoned).

BACKGROUND OF THE INVENTION

The instant invention relates to biocidal coating compositions,particularly paints, in which hydrated lime is used as a biocidal agentand to method of making certain such compositions and paints.

Hydrated lime is well known as a disinfectant, biocidal, and biostaticagent. Its effectiveness for these purposes is based on its highalkalinity, a pH above about 11. In order to retain its biocidalactivity after application to a desired surface, a hydrated lime mustretain the high alkalinity necessary to kill microorganisms.

Unfortunately, hydrated lime is highly susceptible to environmentalattack, primarily by carbon dioxide present in the ambient atmosphere.Carbon dioxide converts the hydrated lime to calcium carbonate, whichdoes not have the alkalinity required to kill microorganisms. Such aconsequence had mitigated against the use of hydrated lime in coatingcompositions, such as paints and whitewash, as effective long termdisinfectants, biocides, or biostatic agents.

The prior parent patent applications first noted above, whose entiredisclosures are hereby specifically incorporated by reference, disclosecoating compositions which have overcome this problem and are effectivecoatings that resist degradation by carbon dioxide for prolonged periodsof time. Such compositions, however, are not truly washable or cleanablewith aqueous materials and their use is thereby limited. Also, as notedtherein, it was not possible to use with such compositions theconventional latex vehicles used in forming paints which employ anionicor quaternary surfactants and emulsifiers.

Most interior building paints are based on a latex vehicle and theirpopularity results from their easy application, much lower odor, and,when dry, a good appearance and appearance retention and ability to becleaned with soap and waer.

As noted in the prior parent applications, such conventional latexbinders were incompatible with hydrated lime which results incoagulation and phase separation almost immediately upon blending withlime.

SUMMARY OF THE INVENTION

The present invention overcomes the problems noted above to providestable biocidal compositions containing hydrated lime and a latex binderthat resists the effects of degradation by the hydrated lime.

Briefly stated, the present invention comprises biocidal film-formingcompositions, particularly paints, comprising a hydrated lime andnon-ionic polyolefinic latex resistant to hydrated lime-inducedcoagulation and phase separation and which maintain their biocidalactivity after being applied to a substrate for extended periods oftime.

The invention also comprises the method of making certain suchcompositions as described below.

DETAILED DESCRIPTION

The compositions of the present invention are particularly suited ascoatings and paints for substrates where the dried coating formed by thecomposition and paint maintains a biocidal activity for extended periodsof time; i.e., at least one month, and preferably for a period of years.

Such activity is desired, for example, in hospitals, nursing homes, foodpreparation facilities (such as factories making food products,restaurants, school cafeterias, and the like), dining facilities, andareas where large numbers of people congregate (such as schools,offices, arenas, and the like) to help eliminate or reduce the spread ofdeleterious microorganisms.

The two essential components of the compositions of the presentinvention are hydrated lime and a non-ionic polyolefinic latex resistantto hydrated lime-induced coagulation and phase separation. Such adverseeffects are due to hydrolysis caused by the lime.

As used herein, the phrase “resistant to hydrated lime-inducedcoagulation and phase separation” means a non-ionic latex resistant tosuch coagulation and phase separation ab initio, or, as herinaftaerdescribed, is treated during admixture with the hydrated lime to preventcoagulation and phase separation.

Examples of ab initio hydrolysis resistant non-ionic polyolefiniclatices are nonester containing non-ionic latices, such asstyrene-butadiene, butadiene-acrylonitrile,butadiene-styrene-acrylonitrile, and chloroprene in non-ionic latexemulsion form or mixtures thereof. Of these, a carboxylatedstyrene-butadiene latex (TYLAC 812 from Reichhold Chemical Co.) ispreferred.

Polyolefinic latices that can be treated during admixture with lime toprevent coagulation and phase separation are the latex copolymerscontaining an ester, such as polyacrylate/ethylene copolymers (such asNANCRYLIC CP3600 from National Starch Co.), polyvinyl acetate/ethylenecopolymers (such as COPOLYMER 525BP or 526BP from Air Products Co.), andpolyvinyl chloride/ethylene copolymers or mixtures thereof.

All of the foregoing non-ionic polyolefinic latices are suitable binderswhich will form films and are suitable for use in forming paints, butpreferred are the non-ester containing latices, in particularcarboxylated styrene-butadiene latex, because they eliminate the needfor the special processing required for ester-containing latices and aremore stable.

To be suitable as a water-washable biocidal film-forming paint theremust be suffucient latex in the composition to form a coherent filmcapable of passing the ASTM tests for resistance to running water(D2247), stain removal (D3258), and sponge cleaning (D4824) and a highratio, on a solids basis, of lime to latex to ensure sustained biocidalactivity.

For paint usage there must also be sufficient latex to enable thefinished biocidal paint to pass the standard ASTM test for 90 degreebending flexure (D522), scratch abrasion resistance (D2486), andindustry tests for resistance to “chalking off”.

The instant compositions and paints can be applied in any of theconventional ways utilized for paints; i.e., brushing, rolling,spraying, and the like.

To accomplish the foregoing purposes there must be at least about 1 partby weight (on a solids basis) of the latex for about 8 parts by weightof the other solids in the paint; i.e., at least about 10 to 11% byweight, on a solids basis for flat paint and, as is known andconventional, larger amounts of latex in enamel or gloss paints. Suchother solids are the hydrated lime, fillers, pigments, and thickeners.It will be understood that the higher the latex solids content of thepaint the longer the “life” of the paint; i.e., the length of time itmaintains its appearance before repainting is required. For a long-lifepaint, such as a 20-year paint, a latex to other solids ratio of 1 to 3is preferred.

For optimum biocidal activity over an extended period of time, at leastone month, the weight ratio of hydrated lime to latex, on a solidsbasis, should be about 1:2 to 1.5:1. While a lower ratio of lime can beused, it is not functionally desirable since it increases the length oftime required to exert its biocidal effect on microorganisms.

In paint formulations the usual and conventional additives in preparingwater-based latex paints are utilized in addition to the hydrated lime.Namely, non-ionic surfactants (alkyl phenol ethers of polyethyleneglycol, such as TRITON X-100 and CF10 from Rohm & Haas, etc.);protective colloids which act as dispersing agents (such as DARACEM 100by W.R. Grace & Co., propylene glycol ester, etc.); fillers or extenders(such as titanium oxide, talc, calcium carbonate, etc.) used to opacifythe latex; a pigment or pigments (all conventional) for the desiredhiding, color, and gloss; coalescing solvents to plasticize the latextemporarily during film formation so that the latex particles coalesce;thickener additives (such as colloidal silica, colloidal clay, lowmolecular weight hydroxypropylmethylcellulose, etc.) to thicken thepaint to promote suspension of the pigment(s) during storage, properrheology for application, and for flow without sagging when the paint isapplied to a surface; anti-foaming agents (such as TROYKYD D-126 fromTroy Chemical Co., silicone fluids, dimethylpolysiloxanes, etc.) tominimize foaming; agents to prevent agglomeration by freezing; and thelike conventional additives. These additives are added in the usualamounts for their usual effects, it being understood that the solidsratio of latex to all solids be as noted above and that the hydratedlime to latex ratio also be as noted.

When a carboxylated styrene-butadiene latex is used as the binder theprocess of making the coating composition is that conventionally used inmaking conventional latex paints. This involves the conventionalgrinding, mixing, and thinning adjustments and, of course, filling thecomposition into suitable containers which are then labeled. Grinding isthe most important step and involves the use of high speed disperserswhich are large tanks equipped with high speed rotating impellers ofvarious shapes. The time and impeller speeds required for grinding,mixing, and the like will, as is known, vary dependent mainly on theparticular components used in making the composition and the processingequipment. The particular times and speeds are readily determined by theconventional procedures used in the paint industry.

The use of these conventional high speed dispersers is especiallycritical when the binder used is a non-ionic polyolefinic ester. Aspreviously noted, if simply admixed with the hydrated lime, such laticeswill coagulate and phase separate either immediately or at most in a fewdays. It has surprisingly been found that if the agitation is continuedafter the latex and hydrated lime are first admixed until hydrolysis ofthe ester group is completed and rheology is stabilized, the admixturewill remain fluid and prevent precipitation of the calcium salt. Theresultant composition will form a less resilient, but suitable, coatingthat is biocidal. The precise length of such mixing will vary dependentupon the particular latex used and ratio of hydrated lime to latex, butcan be readily determined by routine experimentation since inadequatelength of mixing will result in gelling and/or precipitation of thecalcium salt, which conditions are readily observable. It has been foundthat such continuous agitation is not effective with the anioniclatices, and they cannot be used to form biocidal coatings with thehydrated lime.

An added benefit of the instant paints is that they offer long termcorrosion resistance. As a result, the conventional corrosion barriercoatings used in water-based latex paint containers are not required forthe instant paints because lime is a well-known corrosion inhibitor foriron-based metals. Also, the instant paints can be used to paintsteel-reinforced concrete surfaces to inhibit carbon dioxide penetrationand consequent loss of the corrosion-inhibiting lime components of theconcrete. This minimizes the corrosion of the steel reinforcement andextends the life of the concrete structure.

While the precise theory is not completely understood, it is believedthat the large amount of hydrated lime in respect to the latexpreviously noted above ensures that the lime content is relativelycontinuous and presents a highly alkaline surface to the coatings formedwhen the composition is applied to a substrate. Soon after application,the exposed hydrated lime carbonates due to atmospheric carbon dioxideand forms a protective layer against carbon dioxide permeation. However,such carbonate layer is made of particulate solids highly permeable towater vapor and intrusion of moisture by capillarity and microorganisms.The hydrated lime just below this permeable layer is thus protectedagainst carbonation and retains its biocidal pH of over 11 for extendedperiods of time; at least one month and, based on accelerated agingtests, for a period of years.

The invention will be futher described in connection with the followingexamples which are set forth for purposes of illustration only.

In the examples that follow all the proportions are in parts by weightof solids unless expressly stated to the contrary. Also, the measurementof the length of time the hydrated lime retained a biocidal alkalinityin the coating as set forth in the examples was measured by anaccelerated aging test. For each composition tested, three Leneta boardswere coated with a 3-4 mil dry thickness of the composition followingthe ASTM test D4941 and each of the boards placed in an impermeableplastic container having a 100% carbon dioxide atmosphere. The pH of theboards is measured weekly with each week of exposure to the 100% carbondioxide atmosphere being equivalent to 64 weeks of exposure toatmospheric carbon dioxide. The draw down on the Leneta boards alsomeasures hiding power.

EXAMPLE 1

A composition was prepared utilizing the following constituents:

Latex (COPOLYMER 525BP) 200 (55% by wt. solids) Dispersing agent(DARACEM 100) 1 Hydrated lime 50 Calcium carbonate 50 Titanium dioxide150 Hydroxypropylmethyl cellulose 6 Non-ionic surfactants: TRITON X-1002 TRITON CF10 1 Antifoaming agent (TROYKYD D126) 0.5 Water 250

The lime, carbonate, dioxide, non-ionic surfactants, and 200 parts ofthe water were first ground in the conventional manner used in makinglatex paints to form a finely dispersed mixture. To the ground mixturewas then added the latex, dispersing agent, and remaining water withcontinuous mixing until the latex is substantially uniformly dispersedthroughout the mixture, followed by addition of the cellulose and thenthe antifoaming agent, again as is usual in making paints.

The mixing is continued until hydrolysis of the ester is completed;i.e., at least about seven days.

The composition is subjected to the accelerated aging test noted aboveand maintains its biocidal activity for a period greater than one month.

EXAMPLE 2

A composition was prepared utilizing the following constituents:

Latex (NANACRYLIC CP 3600) 200 (51% by wt. solids) Propylene glycolester 5 Hydrated lime 100 Calcium carbonate 100 Titanium dioxide 100Non-ionic surfactant (TRITON X-100) 1 Water 200

The processing set forth in Example 1 was followed except that nothickener or antifoaming agent was used and mixing was not continuedafter the time thorough mixing of the constituents was completed.

The result was that a stiff fluid formed within 24 hours which wasunsuitable as a coating-forming composition.

EXAMPLE 3

A composition was prepared utilizing the following constituents:

Latex (NANACRYLIC CP 3600) 200 Dispersing agent (DARACEM 100) 1 Hydratedlime 50 Titanium dioxide 50 Non-ionic surfactants: TRITON X-100 1 TRITONCF10 0.5 Water 250

The procedure of Example 1 was followed except that the mixing wascontinued until hydrolysis of the ester was completed, about one week.The result was a stable composition that did not thicken into anunusable form and which maintained its biocidal activity for over 8.6years when tested using the accelerated aging test noted above.

EXAMPLE 4

The composition and processing set forth in Example 1 are followed,except that an equivalent amount of a non-ionic polyvinylchloride/ethylene copolymer (in % by wt. solids) is substituted for thepolyvinyl acetate/ethylene copolymer used therein.

A suitable paint composition is formed which maintains its biocidalactivity for over one month when subjected to the noted acceleratedaging test.

EXAMPLE 5

A composition was prepared utilizing the following constituents:

Latex (TYLAC 812) 200 (43.5% by wt. solids) Propylene glycol ester 5Hydrated lime 100 Calcium carbonate 50 Titanium dioxide 100Hydroxypropylmethylcellulose 5 Non-ionic surfactant (TRITON X-100) 1Antifoaming agent (TROYKYD D126) 0.5 Water 200

The constituents were ground and admixed as set forth in Example 1except that no mixing was required after the time thorough admixing ofthe constituents was completed.

The composition was then subjected to the aforenoted accelerated agingtest and as of the date of filing of the instant application stillmaintained its biocidal activity; a period equivalent to just over 3.5years.

EXAMPLES 6-9

The composition and processing of Example 5 are followed except thatseparately each of the following non-ionic latex emulsions aresubstituted in an equal part by weight for the TYLAC 812;butadiene-acrylonitrile, butadiene-styrene-acrylonitrile, andchloroprene.

In each instance excellent stable paints are formed which, when appliedto surfaces, maintain their biocidal activity for a period of at leastone month.

While the invention has been described in connection with a preferredembodiment, it is not intended to limit the scope of the invention tothe particular form set forth but, on the contrary, it is intended tocover such alternatives, modifications, and equivalents as may beincluded within the spirit and scope of the invention as defined by theappended claims.

What is claimed is:
 1. A biocidal film-forming composition comprisinghydrated lime and a non-ionic polyolefinic latex resistant to hydratedlime-induced coagulation and phase separation, wherein said lime andsaid latex are present in a ratio sufficient to maintain the biocidalactivity of said lime for a period of at least one month when thecomposition is applied as a film to a surface.
 2. The composition ofclaim 1 wherein said latex comprises at least about 10% by weight of thetotal solids in the composition.
 3. The composition of claim 1 whereinthe ratio of hydrated lime to latex, in parts by weight of solids, isfrom about 1:2 to 1.5:1.
 4. The composition of claim 1 wherein saidlatex is ab initio resistant to hydrated lime-induced coagulation andphase separation.
 5. The composition of claim 4 wherein said latex is astyrene-butadiene, butadiene acrylonitrile,butadiene-styrene-acrylonitrile, or chloroprene in non-ionic latex formor a mixture thereof.
 6. The composition of claim 5 wherein said latexis a carboxylated styrene-butadiene latex.
 7. The composition of claim 1wherein said latex is a non-ionic latex copolymer containing an ester.8. The composition of claim 7 wherein said latex is apolyacrylate/ethylene copolymer, polyvinyl acetate/ethylene copolymer,polyvinyl chloride/ethylene copolymer, or mixture thereof.
 9. Thecomposition of any one of claims 1 to 8 in the form of a paintcontaining at least one pigment.
 10. A biocidal film-forming paintcomprising a hydrated lime, a non-ionic polyolefinic latex resistant tohydrated lime induced coagulation and phase separation, at least onepaint filler, and at least one paint pigment, wherein said lime and saidlatex are present in a ratio sufficient to maintain the biocidalactivity of said lime for a period of at least one month when the paintis applied as a film to a surface.
 11. The paint of claim 10 whereinsaid latex comprises at least 10% by weight of the total solids in saidpaint.
 12. The paint of claim 10 wherein the ratio of hydrated lime tolatex, in parts by weight of solids, is from about 1:2 to 1.5:1.
 13. Thepaint of claim 10 wherein said latex is ab initio resistant to hydratedlime-induced coagulation and phase separation.
 14. The paint of claim 13wherein said latex is a styrene-butadiene, butadiene acrylonitrile,butadiene-styrene-acrylonitrile, or chloroprene in non-ionic latex formor a mixture thereof.
 15. The paint of claim 14 wherein said latex is acarboxylated styrene-butadiene latex.
 16. The paint of claim 10 whereinsaid latex is a non-ionic latex copolymer containing an ester.
 17. Thepaint of claim 16 wherein said latex is a polyacrylate/ethylenecopolymer, polyvinyl acetate/ethylene copolymer, polyvinylchloride/ethylene copolymer, or mixture thereof.
 18. The paint of claim10 wherein the latex is a carboxylated styrene-butadiene comprising atleast about 10% by weight of the total solids in the composition and inwhich the ratio of hydrated lime to latex, in parts by weight of solids,is from about 1:2 to 1.5:1.
 19. The method of making a biocidalfilm-forming composition comprising admixing hydrated lime and anon-ionic polyolefinic ester latex with agitation and continuing suchagitation until hydrolysis of the ester is substantially completed andrheology of the composition is stabilized.
 20. The method of claim 19 inwhich the latex is a polyacrylate/ethylene copolymer, polyvinylacetate/ethylene copolymer, polyvinyl chloride/ethylene copolymer, ormixture thereof.
 21. The method of claim 19 wherein the latex comprisesat least about 10% by weight of the total solids in the composition andthe ratio of hydrated lime to latex, in parts by weight of solids, isfrom about 1:2 to 1.5:1.
 22. The paint of claim 10 including athickener.
 23. The paint of claim 22 wherein the thickener is acellulosic polymer.
 24. The composition of claim 1 wherein thecomposition maintains its biocidal activity for a period of years whenthe composition is applied as a film to a surface.
 25. The paint ofclaim 10 wherein the paint maintains its biocidal activity for a periodof years when the paint is applied as a film to a surface.